Susanne M. Scheierling

Towards an agenda for improving wastewater use in agriculture

This paper sets out the trends and challenges of wastewater use in agriculture; identifies the risks and benefits of wastewater irrigation; describes the risk-assessment and management framework adopted by the World Health Organization, the Food and Agriculture Organization of the United Nations and other international and national organizations; and proposes measures for applying the framework to reduce health risks by moving from unplanned to a planned, integrated, approach to wastewater use for irrigation.

How to Assess Agricultural Water Productivity? Looking for Water in the Agricultural Productivity and Efficiency Literature

Given population and income growth, it is widely expected that the agricultural sector will have to expand the use of water for irrigation to meet rising food demand; at the same time, the competition for water resources is growing in many regions. As a response, it is increasingly recommended that efforts should focus on improving water productivity in agriculture, and significant public and private investments are being made with this goal in mind. Yet most public communications are vague on the meaning of agricultural water productivity, and on what should be done to improve it. They also tend to emphasize water as if it were the only input that mattered. This paper presents findings from a first attempt to survey the agricultural productivity and efficiency literature with regard to the explicit inclusion of water aspects in productivity and efficiency measurements, with the aim of contributing to the discussion on how to assess and possibly improve agricultural water productivity. The focus is on studies applying single-factor productivity measures, total factor productivity indices, frontier models, and deductive models that incorporate water. A key finding is that most studies either incorporate field- and basin-level aspects but focus only on a single input (water), or they apply a multi-factor approach but do not tackle the basin level. It seems that no study on agricultural water productivity has yet presented an approach that accounts for multiple inputs and basin-level issues. However, deductive methods do provide the flexibility to overcome many of the limitations of the other methods.

Assessing the direct economic effects of reallocating irrigation water to alternative uses : concepts and an application

Irrigation water reallocations are playing an increasingly important role in both developed and developing countries. With growing urban and environmental water demands, rising costs for the development of new water supplies, and irrigated agriculture usually including the least economically valuable use of water, transfers of irrigation water to alternative uses are increasing. However, such reallocations are often controversial, and it is often questioned whether the benefits resulting from these transactions are large enough to outweigh the associated costs. This paper reviews the experience with irrigation water transfers, including the involvement of the World Bank. It discusses the problems of assessing the direct economic effects of reallocations, with a focus on the foregone direct benefits in irrigated agriculture. Because foregone direct benefits cannot easily be directly observed, they need to be estimated. However, assessments have shown widely differing estimates -- even when the same methodology was used. The paper reviews the methodologies and model specifications used for estimating foregone direct benefits; illustrates the impact of different model specifications on the magnitude of estimates of foregone direct benefits based on an application in an example case; and draws conclusions with regard to future efforts in assessing reallocation effects, including calculating adequate compensation for farmers. Because estimating the direct benefits of irrigation expansion is methodologically equivalent to estimating foregone direct benefits from reduced irrigation water supplies, the findings have implications for a broader range of water allocation decisions.

Beyond 'More Crop per Drop'

This report aims to provide key highlights from two decades of IWMI research and the broader irrigation literature on agricultural water productivity, with an emphasis on the evolution and application of the concept, highlighting its contributions and limitations while identifying opportunities for further refinements in the way it is understood and applied. Chapter two describes the origins of the concept of agricultural water productivity and its methodological developments. Chapter three illustrates the different ways the concept has been operationalized in applied research, offers a description of the pathways—with their associated interventions, for improving water productivity, and discusses the contributions to broader development objectives. Based on these, and considering the broader literature, Chapter four presents a set of key lessons and insights from two decades of research on water productivity. Chapter five concludes by highlighting how a focus on agricultural water productivity has brought greater attention to critical water scarcity and management issues. Important strategic opportunities remain, however, for continued improvements in technologies and management practices, data sources, and interdisciplinary research to develop and apply more comprehensive approaches to address water scarcity concerns and, ultimately, make progress towards broader development objectives.

Water Productivity in Agriculture: Looking for Water in the Agricultural Productivity and Efficiency Literature

Expectations are that the agricultural sector will have to expand the use of water for irrigation to meet rising food demand, given population and income growth. At the same time, the competition for water resources is growing in many regions. Increasing water productivity in agriculture is widely seen as a critical response to help address these challenges. Yet much of the public debate is vague on the meaning of agricultural water productivity—often emphasizing “more crop per drop” as if water were the only input that mattered—, and approaches for assessing and increasing water productivity are seldom addressed systematically. This paper discusses conceptual issues that should be kept in mind when assessing agricultural water productivity, and presents findings from what may be the first survey of the agricultural productivity and efficiency literature with regard to the explicit inclusion of water aspects in productivity and efficiency measurements. The survey includes studies applying single-factor productivity measures, total factor productivity indices, frontier models, and deductive models. A key finding is that most studies either incorporate field- and basin-level aspects but focus only on a single input (water), or they apply a multi-factor approach but do not tackle the basin-level aspects. It seems that no study on agricultural water productivity has yet presented an approach that accounts for multiple inputs and basin-level issues. However, deductive methods provide the flexibility to overcome some of the limitations of the other methods.

Beyond crop per drop : assessing agricultural water productivity and efficiency in a maturing water economy

Water scarcity is seen as a major risk in many parts of the world, and water crises are consistently cited as among the top global risks. Irrigated agriculture is by far the largest water use worldwide, accounting for an estimated 70 percent of total freshwater withdrawals. In many drier countries, agricultural water use accounts for more than 90 percent of total withdrawals. As water becomes increasingly scarce, the management of agricultural irrigation moves to the center of water management concerns. Without advances in management and more integrated policy making in both developed and developing countries, water scarcity and related water problems will significantly worsen over the next several decades. Yet the question of how best to adapt agricultural water management is complicated, not least because irrigated agriculture is at the center of two large and conflicting trends. This report aims to shed further light on these issues: first, by clarifying some of the underlying concepts in the discussion of agricultural water productivity and efficiency; second, by reviewing and analyzing the available methods for assessing water productivity and efficiency; and, third, by discussing their application and relevance in different contexts. As the background for this analysis, the report highlights the central role of water use in irrigated agriculture and its link with increasing water scarcity. This is discussed in the context of the transition from an expansionary water economy to a mature water economy. The report further develops this framework to reflect water management issues in irrigated agriculture. The expansionary phase is characterized by readily available water supplies to meet the growing demand for irrigation water as agricultural production increases. In the mature phase, the intensifying competition for water tends to be perceived as an increasing scarcity of water. In the transition from the expansionary phase to the mature phase, the interdependencies among water users increase, and the hydrologic setting and the rising externalities need to be considered. The policy objective of increasing agricultural production needs to be balanced with the new objective of water conservation. The interventions, which in the expansionary phase were focused on engineering and technological interventions to expand agricultural water supplies, need to increasingly incorporate demand-side interventions and options for reallocations, and to further develop context-specific policy and institutional arrangements as the water economy matures.